Dieting has been attempted by a lot of people in weight controlling and weight loss. One dieting approach is to increase the consumption of dietary fibers. It has been shown that there is an inverse relationship between the dietary fiber consumption and weight gain (JAMA. 1999 Oct. 27; 282(16):1539-46.). A lot of dietary fiber supplements are available including alginate, chitosan, pectin, etc.
Alginate is a dietary fiber supplement from seaweeds. Alginate is an anionic polysaccharide with carboxyl groups with pKa from 1.5 to 3.5. Alginate is available in alginic acid and its salt forms including sodium alginate, potassium alginate, calcium alginate, etc. Alginate solution can form gel in the gastric pH or in the presence of calcium or other multivalent ions.
Chitosan is a dietary fiber supplement from shrimp shell. Chitosan is a cationic polysaccharide with amine groups with pKa around 6.5. Chitosan can dissolve in acidic solution. Chitosan oligosaccharide is a type of chitosan with low molecular weight, usually with molecular weight less than 5000. Especially, if the chitosan oligosaccharide has a molecular weight less than 2000, then the chitosan oligosaccharide can dissolve in pure water or even in basic aqueous solutions. In addition, modifications can be made to the chitosan molecule to improve its solubility in water. For example, glycol chitosan is the addition of ethylene glycol group to the chitosan; even with high molecular weight, glycol chitosan can dissolves in pure water and also in basic solutions.
U.S. Pat. No. 2,935,447 (1960) disclosed that taking alginate solution alone or taking alginate solution in combination with some insoluble calcium salts can be used as an appetite depressant. U.S. patent No. 2010/0009932 A1 disclosed that alginate in combination with pectin can form gel in gastric pH for enhancing satiety. U.S. patent No. 2007/0087038 A1 disclosed that addition of a slow releasing acidifying agent into the mixture of alginate with an insoluble calcium salt can promote the gel formation which is less dependent on the gastric pH.
A 12-week clinical study (Am J Clin Nutr doi: 10.3945/ajcn.111.025312) showed that using alginate solution in combination with calcium salt as a preload before meal was more effective to cause weight loss than a placebo preload in obesity patients. The clinical study observed significant side effects such as abdominal pain and distention in the alginate testing group. This could be due to that calcium salts and alginate polymers form gel structure under gastric condition in the stomach, but the formed gel structure is not reversible under an intestinal pH (6.8 to 7.5) and would maintain the gel structure after the gel moving into the intestine, thus cause the abdominal pain and distention. In addition, the using of calcium salts as the gelling ions, especially if the alginate preload being administered three times a day, the amount of calcium intake could exceed the daily upper limit for the calcium suggested from the Office of Dietary Supplement from the National Institute of Health.
The present invention provides a composition of dietary fiber supplements whose aqueous solution can form a gel structure in an acidic condition and the formed gel structure can be reversed back to a solution state in an intestinal pH condition.